Vertical tapeline microwave coupler for paramagnetic spin resonance

ABSTRACT

A device for coupling RF energy for use in magnetic spin resonance which includes a series of rectangular solids constructed of paramagnetic material. An electrically conducting folded ribbon is interleaved between the rectangular solid in the longitudinal direction. The ribbon and the rectangular solids are in surface contact with each other and the rectangular solids are in surface contact with upper and lower ground planes.

United States Patent [1 1 Lewis 1 1 VERTICAL TAPELINE MICROWAVE COUPLER FOR PARAMAGNETIC SPIN RESONANCE [75] Inventor: Owen Lewis, Syracuse, NY.

[73] Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, DC.

22 Filed: May 19, 1971 21 App1.No.: 144,956

[52] US. Cl. 333/82 R, 333/82 A, 333/82 B, 333/84 M [51] Int. Cl H0lp 7/00, H0lp 7/02, H0lp 3/08 [58] Field of Search 333/84 M, 84 R, 24.1, 333/242, 31 R, 99 R; 340/173 NC [5 6] References Cited UNITED STATES PATENTS 2,887,673 5/1959 Hahn 340/173 N1 3,022,472 2/1962 Tanenbaum et a1. 333/84 M 3,072,890 1/1963 Smith et a1. 340/173 Nl 3,155,941 11/1964 Mims 340/173 NI 3,447,143 5/1969 Hair et a1. 333/84 M 3,500,263 3/1970 Adam et a]... 333/84 M 3,521,198 7/1970 Shahbender..... 333/24.1 X 3,593,159 7/1971 Kaplan et a1 333/31 R OTHER PUBLICATIONS Hewitt, H. S., A Computer Designed, 720 to 1 Microwave Compression Filter, MTT-l5, 12-1967, pp.

[ June 26, 1973 Nano4econd S. H., A Miniature Monostrip Delay Line for Nano-Second Pulses, Electrical Design News,

Hyltin, T. M., Microstrip Transmission on Semiconductor Dielectrics MTT-13-l l-l965, pp. 777-781. Lehrfeld, S. 8., What If You Dont Use Alumina! Microwaves 3-1971, pp. 54-56.

Gordon et al., Microwave Spin Echoes From Donor Electrons in Silicon, Physical Rev. Letters, Vol. 1 No. 10-11-1958, pp. 368-370 Bozanic et al., Spectrum Analysis of Spin-Echo Signals in Iron Doped Rutile, Jr. of Applied Physics, Vol. 40, 2-1969 pp. 881-884.

Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Wm. H. Punter Attorney-Harry A. Herbert, Jr. and Julian L. Siegel [57] ABSTRACT 4 Claims, 1 Drawing Figure VERTICAL TAPELINE MICROWAVE COUPLER FOR PARAMAGNETIC SPIN RESONANCE BACKGROUND OF THE INVENTION This invention relates to microwave coupling devices, and more particularly to vertical tapelines.

There has been a need in the past to couple microwave energy efficiently to the spin system of the paramagnetic host over a broad bandwidth. Cavity structures are inherently narrowband and, as such, are inadequate. One possibility is to apply existing slow-wave structure technology to the problem. However, the planar designs of microstrip and stripline devices which are used extensively in microwave circuits are unsatisfactory. The objections are that bandwidths are too wide, i.e., the field can be made more intense without sacrificing operation bandwidth which is well known in the maser art. Also, resistive loss for long lengths is prohibitive, and microwave energy is not coupled strongly because the region of strongest interaction cannot contain the active paramagnetic material, particularly in the case of stripline. To overcome these objections, this invention utilizes the concept of the vertical tapeline.

SUMMARY OF THE INVENTION The present invention is used in the spin resonance phenomena of paramagnetic materials to produce a correlator of microwave signals. To function in the various correlator modes, the paramagnetic material must be placed in a suitable coupling structure which couples RF energy to the magnetic spin resonance system of the paramagnetic material. Such structures can be a simple tuned L-C oscillator for low frequency operation, or a resonant cavity vertical tapeline spin echo module for microwave frequency operation. The vertical tapeline spin echo module which is presented here provides an improved spin echo correlator configuration. This configuration is a type of slow wave structure which is designed on the basis of modifying available equations.

It is therefore an object of this invention to provide a novel magnetic spin resonant device for coupling RF energy.

It is another object to provide a magnetic spin resonant device which has a minimum resistance loss.

It is still another object to provide a coupling device for RF energy that has definite bandwidth control.

These and other advantages, features and objects of the invention will become more apparent from the fol lowing description taken in connection with the illustrative embodiment in the accompanying drawing.

DESCRIPTION OF DRAWING The sole FIGURE is a perspective view of a vertical tapeline coupling device which is an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring to the FIGURE, there is shown a vertical tapeline which consists of conducting ribbon 1 I wound among blocks 13 which are constructed of paramagnetic material which can be of magnesium doped titanate or doped silicon. The end surface of blocks 13 have the dimensions of p X b, p being the pitch. The width of conducting ribbon 11 is designated as w. The portion of blocks 13 not in contact with conducting ribbon 11 is designated as d. The desired length of blocks 13 is M4. Paramagnetic blocks 13 and conducting ribbon 11 are sandwiched between ground planes 15 and 17.

The broad faces of conductor 11 produce a high capacitance giving a strong coupling without reducing the pitch, p, as is required with planar structures. This allows for definite bandwidth control, thus maximizing intensity of the microwave field to the particular mission requirements. Also, the large surface area reduces resistive losses so that the overall length, I, can be extremely long as compared to stripline. In addition, all of the RF fields are coupled to the active material through the high capacitance thereby producing a large filling factor which is almost unity. As an example, a vertical tapeline using a polycrystalline magnesium titanate with Mn paramagnetic centers operating in S- band frequencies has a twenty percent bandwidth.

What is claimed is:

l. A broadband microwave cavity coupler comprismg:

a. a series of rectangular solids made of paramagnetic material and having the longitudinal axis thereof in parallel alignment;

b. an electrically conducting ribbon longitudinally interleaving the rectangular solids and being in surface contact therewith; and

0. upper and lower conducting planes in surface contact with the rectangular solids and serving as ground planes.

2. A broadband microwave cavity coupler according to claim I wherein the length of the rectangular solids is one-fourth of the microwave wavelength.

3. A broadband microwave cavity coupler according to claim 2 wherein the paramagnetic material is doped silicon.

4. A broadband microwave cavity coupler according to claim 2 wherein the paramagnetic material is doped magnesium titanate.

lk l I 

1. A broadband microwave cavity coupler comprising: a. a series of rectangular solids made of paramagnetic material and having the longitudinal axis thereof in parallel alignment; b. an electrically conducting ribbon longitudinally interleaving the rectangular solids and being in surface contact therewith; and c. upper and lower conducting planes in surface contact with the rectangular solids and serving as ground planes.
 2. A broadband microwave cavity coupler according to claim 1 wherein the length of the rectangular solids is one-fourth of the microwave wavelength.
 3. A broadband microwave cavity coupler according to claim 2 wherein the paramagnetic material is doped silicon.
 4. A broadband microwave cavity coupler according to claim 2 wherein the paramagnetic material is doped magnesium titanate. 